1. Technical Field
The present invention relates to an electro-optical device including an electro-optical panel in which a plurality of electro-optical elements, such as electro-luminescent elements (EL) or a plurality of light valves is arranged, an image forming apparatus using the electro-optical device, and a method of manufacturing the electro-optical device.
2. Related Art
As for a line-printer head which records an electrostatic latent image on an image carrier, for example a photoconductor drum of an elect-photographic image forming apparatus, techniques using an electroluminescent element (EL) array has been developed. JP-A-2006-205430 discloses one of such techniques, in which a converging lens array is disposed between an EL element array and an image carrier. A well-known converging lens array is a SELFOC lens array (“SELFOC” is a trademark) available from Nippon Sheet Glass Co., Ltd. In the converging lens array, each refractive index distribution type lens is constituted by a graded index optical fiber having a graded refractive index profile in which the refractive index is the lowest at a central axis thereof and becomes higher as it becomes farther from the central axis. The converging lens array allows light from an EL element array to pass therethrough so that an erect image with respect to an image on the EL element array can be imaged on the image carrier. The image imaged on the image carrier by using a plurality of refractive index distribution type lenses constitutes a single continuous image.
JP-A-2006-218848 discloses a technique in which a light transmissible spacer is arranged between an EL element array and a converging lens array in order to reduce loss of light from EL elements. With such a structure, a diameter of light beam emitted from the EL elements and advancing toward the lens array is smaller than that in a structure with no spacer but air between a light source array and a lens array. Accordingly, it is possible to increase the ratio (the efficiency of light utilization) of quantity of light from the light source array to quantity of light incident on the lens array.
As for the printer head, it is desirable that the optical characteristics of spots of the image carrier on which light from the EL elements is irradiated is even when the plurality of EL elements emits light. That is, a spot irradiated by light from a certain EL element and a spot irradiated by light from another EL element preferably have almost the same optical characteristics.